Grado cartridge-How to identify

I have a Grado RS cartridge. I purchased it awhile back and was told it was a Reference Signature. I think it may be a Reference Sonata. It has RS scribed in the top and K97 in the plastic by the pins. Also what appears to be a "s" on the underside.
RS on the wood body = Reference Sonata.
S scribed on the metal of the inner "works" = Sonata